Vehicle engines generally comprise certain accessories that are used in the operation of the engine and vehicle. Such accessories can include a power steering pump, an air conditioning compressor, an alternator, an oil pump, a fuel pump and so on. These accessories are generally driven by a serpentine belt. The serpentine belt engages a pulley on each accessory as well as on an engine crankshaft. The engine crankshaft provides the torque to drive the accessories.
As the belt is driven by the crankshaft it is necessarily subject to engine speed variations during acceleration and deceleration of the vehicle. In other words the operating speed of the accessories is directly proportional to the speed of the engine. The variations in engine speed, particularly engine speeds greater than idle, result in inefficient operation of the accessories because each accessory must be designed to operate satisfactorily over the entire engine speed range. This necessarily means that the efficiency is less than optimum for most of the engine speed range. Therefore it is desirable to decouple some or all of the accessories from the engine crankshaft so they can be driven at a lower and narrower optimum speed range. Further, operating the accessories at relatively higher speeds places a greater load on the engine than if they are operated at a slower speed.
Representative of the art is U.S. Pat. No. 4,862,770 (1989) to Smith which discloses a two-speed gear box adapted to be mounted on the face of an automobile accessory, such as an automotive alternator to increase the speed of the alternator on demand.
The clutch assembly disclosed in Smith comprises a brake band encompassing an outer cylindrical surface. The brake band is operated with mechanical vacuum means which engage or disengage the brake band. Such a system can be adversely affected by loss of vacuum, for example by vacuum hose failure, or by contamination on the cylindrical surface between the brake band and the cylindrical surface.
The prior art transmissions are designed to proportionately reduce the speed of the driven accessories as the engine speed increases above idle. This reduces the accessory power requirement. However, at idle the accessories are operated on a 1:1 basis with no speed reduction as compared to engine speeds above idle.
In recent years, an automatic engine stopping and starting apparatus has been known for stopping an engine after a running vehicle has been stopped and restarting the engine if conditions for driving the vehicle have been satisfied again. The automatic engine stopping and starting apparatus is arranged such that fuel supply to the engine is interrupted while the vehicle is stopped, resulting in reduced fuel consumption.
Representative of the art is U.S. Pat. No. 6,048,288 (2000) to Tsujii et al. which discloses a system that operates a motor when a vehicle is stopped by providing a connection switching unit disposed between the drive shaft of the engine and a rotational shaft of the motor to enable/disable power transmission between the drive shaft of the engine and the rotational shaft of the motor, and a transmission controller that controls a function of the connection switching unit for enabling/disabling power transmission. When an auxiliary machine is operated by a motor while the engine is stopped, control is performed such that rotation of the rotational shaft of the motor is not transmitted to the drive shaft of the engine. The auxiliary machine is operated by the motor without operating the engine.
What is needed is a belt drive system that controls an accessory speed with respect to an engine speed by a combination of a two speed transmission ratio and output pulley and accessory pulley ratio. What is needed is a two speed transmission comprising an electromagnetic brake controlled with respect to an engine condition. What is needed is a two-speed transmission having coaxial input and dual outputs. What is needed is a motor generator system that has a speed reducing unit disposed between the engine and a motor generator. The present invention meets these needs.